1. Field of Embodiments
The present embodiments relate generally to occlusion devices that are for use in the left atrial appendage (“LAA”) or other suitable treatment sites.
2. Description of Related Art
The LAA is the small conical projection from the upper anterior portion of the left atrium. Blood pooling in the LAA may arise spontaneously or as a result of atrial fibrillation. When blood pools in the LAA, blood clots can form. The migration of clots from the LAA to the bloodstream can cause serious problems when the clots embolize in the arterial system. More than 90% of clots formed during atrial fibrillation are formed in the LAA. Sievert et al., CIRCULATION 105:1887-1889 (2002). Embolization of these clots is a frequent cause of stroke. Thus, prevention of clot formation in, or clot migration from, the LAA may reduce the occurrences of stroke in patients with atrial fibrillation.
A common method of reducing the risk of clot formation is treatment with anticoagulants such as warfarin. Such treatment has been an effective method of reducing the incidence of stroke. However, strokes may still occur in patients using anticoagulants if there is a necessary or inadvertent lapse in treatment. Also, many patients who are at risk of stroke are contraindicated from using anticoagulants. Anticoagulant treatment is effective, but the difficulty in treating patients continuously and the high occurrence of contraindication give rise to a need for a different treatment option.
Another method of treatment designed to reduce clotting and embolization leading to stroke is LAA obliteration. Clearly, obliteration of the LAA will lead to less clotting during atrial fibrillation. Obliteration may occur during open cardiac surgery or via a less invasive thoracoscopic procedure. Many patients with a high risk of stroke are not candidates for such procedures because of their compromised health status. Further, obliteration of the LAA may have adverse haemodynamic and hormonal effects that have not been fully studied. See Al-Saady et al., HEART 82:547-554 (1999).
The limitations of anticoagulant treatment and surgical obliteration of the LAA give rise to the need for a less invasive method and device to aid in preventing migration of clots from the LAA into the bloodstream.
Various devices have been developed and used for LAA occlusion. One such device includes a Nitinol cage enclosed in an ePTFE membrane. The device is designed to be inserted entirely into the LAA and has multiple anchors for attachment to the interior wall of the LAA. Because the device is designed to be inserted entirely into the LAA, the device must be properly sized to ensure complete occlusion of the LAA. Improper measurement of the LAA may lead to increased implantation times or decreased effectiveness of the device if the wrong size is implanted.
Another device includes a wire cage partially covered by an ePTFE membrane. This device is also designed to be inserted entirely within the LAA and includes no anchors for attachment within the LAA. As above, improper measurement of this device may result in increased implantation times or decreased effectiveness. Also, the lack of an anchoring mechanism allows migration of the device, which may lead to more serious complications if the device migrates out of the LAA.
Thus, the shortcomings of the existing devices may lead to longer procedures, incomplete occlusion of the LAA or other serious complications triggered by migration of the device out of the LAA. Furthermore, existing devices are oversized, potentially causing stretching of the LAA. For example, existing devices may be larger than the LAA by 20-25%. Such stretching may lead to life threatening perforation, erosion, arrhythmia or compression of circumflex coronary artery. The circumflex coronary artery is in close proximity to the orifice of the LAA.
A need exists for an improved LAA occlusion device and method for LAA occlusion, including a LAA occlusion device and method for LAA occlusion that may addresses one or more of the above described disadvantages. For example, a need exists for a LAA occlusion device and method that ensures complete occlusion or substantially complete occlusion of the LAA to aid in the prevention of clot formation and clot migration from the LAA in order to reduce the risk of stroke in patients with atrial fibrillation. Additionally, a need exists for a LAA occlusion devices that is effectively anchored to the musculature of the LAA to prevent excessive movement of the device or migration of the device out of the LAA, with minimal intentional penetration of the LAA. A need also exists for a LAA occlusion device that will provide complete occlusion or substantially complete occlusion of the LAA independent of the physiology of the patient in order to reduce implantation times and reduce complications caused by an oversized device.